Engine starter



Oct. 7, 1947.

J. E. BUXTON ENGINE STARTER Filed Dec. 21, 1945 WITNESS Patented Oct. 7,1947 ENGINE STARTER James E. Buxton, Elmira, N. Y., assignor to BendixAviation Corporation, Elmira Heights, N. Y., a corporation of DelawareApplication December 21, 1945, Serial No. 636,373

Claims.

The present; invention relates to an engine starter and moreparticularly to that type of starter in which the mechanism remainsoperatively connected to the engine to be started until said engine isproperly self-operative.

It is an object of the present invention to provide a novel enginestarter of the above type which is simple and economical in constructionand easy to assemble.

It is a further object to provide such a device in which the frictionbetween the actuating and. control members for the engine driving memberis increased through the action of centrifugal force to resist thedisengaging movement of the engine driving member when momentary orisolated impulses are received from the engine during cranking.

It is a further object to provide such a device in which a ring ofmaterial having a high coeflicient of friction is placed between theactuating and control members in position to engage and frictionallyclutch said members together when the control member is misaligned bycentrifugal force.

It is a further object to provide such a device wherein the controlmember is provided with means for cocking or moving it out of alignmenton the actuating member responsive to centrifugal force to thereby causethe control member to bind frictionally on the actuating member.

- Further objects and advantages will be apparent to those skilled inthe art from the following description and accompanying drawing, inwhich:

Fig. 1 is a side elevation partly in section of a preferred form of thepresent invention shown inidle position;

Fig. 2 is a view similar to Fig. 1 showing the starter drive inoverrunning position;

Fig. 3 is a detail view in perspective of the actuating member of thestarter, with the anti-drift means partly broken away;

Fig. 4 is a side elevation partly in section of a form of the actuatingmember embodying a friction ring; and

Fig. 5 is a perspective view of the casing and clutch housing membersshowing the method of assembly.

In Fig. 1 of the drawing, there is illustrated a power shaft l, whichmay be the armature shaft of an electric motor, not shown, having asmooth reduced extension l providing a stop shoulder 2 against whichthrust washers 2' are seated. An actuating member in the form of a screwshaft 3 is fixed thereon in any suitable manner as by means of the drivepin 4 extending through the power shaft, and retained therein bysuitable means such as a set screw 4'. A control member in the form of anut 5 is threaded on the screw shaft 3. An engine driving member in theform of a pinion 6 is slidably journalled on the reduced portion 1' ofthe power shaft I in position to engage and rotate an engine member suchas a gear I when the pinion is pressed into cranking position againststop shoulder 2. A yielding driving connection between the control nutand pinion is provided comprising a yielding member in the form of asleeve 8 of elastically deformable material such as rubber seated on thecontrol nut 5 against a flange 9, and a normally engaged 'overrunningclutch comprising a driving clutch plate I! having saw-tooth dentals l2and a driven clutch plate l3 having similar dentals l4. Driving plate IIis demountably attached to a barrel or casing member l5 by means of interal lugs l6 fitted within longitudinal slotsl'! in the barrel and heldtherein by a combination lock member and clutch housing member l8. Thedriven plate I3 is fixed in any suitable manner such as welding at H] tothe pinion 6 and is held in contact with the driving plate H by a spring21 seated at one end against a shoulder 22 on the periphery of plate l 3and bearing at the other end against the radial flange 23 of clutchhousing l8. The rear of barrel I5 is formed with an inwardly extendingrib 24 against which the flange 9 of the control nut 5 rests with aslight pressure imparted thereto by the initial compression of rubbersleeve 8.

According to the present invention, means are provided for inclining ormisaligning the control nut 5 on the screw shaft 3 responsive tocentrifugal force so as to cause the control nut to bind frictionally onthe screw shaft and thereby resist traversal thereon when the parts arerotating at high speed. For this purpose, suitable clearance is providedbetween the threads 21 and 28 on the nut and screw shaft respectively,the nut is counterbored at its rear end as shown at 25, and an eccentricmass 26 is formed thereon. The thread clearance is so chosen inconjunction with the l-engthof the threads 21 as to permit substantialmisalignment of the parts so as to cause a progressive increase in theinter-thread friction as the .rotative speed of the control nut 5increases at the moment when the engine fires.

Anti-drift means for the pinion 6 while in idle position are provided inthe form of a pin 29 held within a radial hole 30 in the eccentricportion .26 of control nut 5. The anti-drift pin 29 is pressed intoarecess 3| in the screw shaft 3 by a spring 32, the upper end of saidspring being seated against a ring 33 which is pressed on the controlnut in position to cover the hole 30 and is provided with an opening 34forming a guide for the pin 29. The location of the anti-drift pin inthe eccentric portion of nut 5 causes the pressur of the pin on thescrew shaft to assist the action of the eccentric mass in causing thecocking action of the nut on the screw shaft.

In the operation of this embodiment of the invention, rotation of thepower shaft I and screw shaft 3 causes the control nut 5 and itsassociated parts to traverse to the right in Fig. 1 pushing the pinion 6into mesh with the engine gear 1 and upon contact of the pinion againstthrust washers 2' to close the clutch II, I3. Further traversal of thecontrol nut -5 compresses the rubber s1eeve8 until sufficient torque istransmitted to the engine gear 1 to cause it to rotate and crank theengine.

When th engine fires, the sudden acceleration of the engine gear ismultiplied by the gear ratio of the gear and pinion andtransmittedthrough the closed clutch I I, I3 to the control nut 5,causing it to overrun and move backward on the screw shaft 3 thusrelaxing the rubber sleeve 8 and allowing the clutch II, I3 to overrun.The high speed of rotation of the control nut at this time causes theeccentric mass 26 thereon to cock the nut on the screw shaft thuscausing the nut to bind and resist traversal back to idle position in amanner similar to the action of the pinion 6 on its screw shaft 4 asshown and described in the patentto Bendix, 1,274,369. The screw 3 whilein idle position. The operation of this form of the invention is similarto that of the first embodiment except that when centrifugal.

force produces misalignment of the nut 5', on the shaft 3, the ring 35is caused to engage and bind frictionally on the tops of the threads ofthe screwshaft. The ring 35 is preferably formed of a material such asrubber, fiber or plastic having a highcoefficient of friction-wherebythe frictional-connection thus established between nut '5' and shaft 3is effective in retarding relative motion therebetween. 1

Although certain embodiments of the invention have-been shown anddescribed in detail, it will 7 be understood that other embodiments arepossible and changes may be made in the formand arrangement of the partswithout departing from the spirit of the invention as definedin theclaims appended hereto.

shaft is also rapidly accelerated by the release 7 of, the crankingload, whereby the nut remains clutched to the screw shaft by the cockingaction of the eccentric mass as long as the operator maintains thestarting switch'closed, and the pinion is consequently held in mesh withthe engine gear.

If the engine should fail to continue. self-operative, the engine gearslows down, retardingthe pinion 6 and its clutch member I3. When thelatter slows down to the speed of they clutch member II, the saw-toothdentals of the. clutch members engage under the action of the spring 2!,whereby the nut 5 is also retarded and'consequently traversed by thescrew shaft to the right in Fig. '1, and cranking is resumed. The engineis thus cranked continuously until it is reliably self-operative. Whenthe engine is properly functioning, the operator deenergizes thestarting motor whereupon the armature shaft I and screw shaft 3 come torest. Th control nut simultaneously slows: down until the cocking effectof the eccentric mass 26 is reduced to the point where the torquetransmitted from the pinion through the overrunning clutch II, I3 issufficient to move the nut back to idle position,

thus drawing the pinion out of mesh'with the engine gear. Thereafter theparts are yieldably maintained in idle position by the engagement ofanti-drift pin 29 in recess 3I in the screw shaft.

In Fig. 4 of the drawing, a second embodiment of the present inventionis shown in Which-the inter-thread friction between the control nut'5"and screw shaft 3 is either augmented or. supplanted by a friction ring35having a high coeflicient of friction interposed between said nut andshaft. The ring 35 may have any suitable location between the nut 5 andshaft 3'but is preferably pressed'into the bore at the forward end ofthe control nut'and held therein in' any desired manner as by friction.The inner diameterv of the ring 35 i -radially spaced from shaft What isclaimed is: 1. In an engine starter, the combination of a power shaft,an actuating member fixed thereon,

a control member having an inclined connection to said actuating member,said connection having means for permitting relative misalignmentbetween said members, an engine driving member Slidably journalled onsaid power shaft for engagement with and rotation of a member of anengine to be started, means for driving said en-- 2. In an enginestarter, the combination oil-a power shaft, a screw shaft fixed thereon,a control nut having a female threadfor a portion of its length mountedonsaid screw shaft with sufficient clearance to permit relativeinclination of the respective aXes of rotation thereof, an enginedriving member slidably journalled on'said'power shaft for movement intoand out of drivingengagement with a member of an engine to be started,means for traversing and rotating said engine driving member from saidcontrol nut,

said means including an overrunning clutch; and

means on said'control nut responsive to centrif ugal force forinclining'said nut on said shaft and thereby increasing the frictiontherebetween :to-resist disengagement of said engine driving member fromthe engine member.

V 3. In an engine starter, the combination of a power shaft, a screwshaft fixed thereon, a control nut loosely threaded on said screw shaftand provided with a counterbore for a substantial part of its length topermit said nutto' tilt out of the axis'of rotation of said shaft, anengine driv ing member slidably journalled; onsaid power shaft forengagement withla'nd rotation of a member of an engine to'bestarted,;means' including a clutch for driving, said enginge drivingmember from said control nut, and means includment of the nut'thereon'to thereby cause the nut to" bind ,frictionaily on thescrewshaft','means on said control nut including an anti-drift memberacting on said screw shaft for producing said misalignment, a pinionslidably journalled on said motor shaft for movement into mesh with androtation of an engine gear, and means including an overrunning clutchand a yieldable member for driving said pinion from said control nut.

5. In an engine starter, the combination of a power shaft, a screw shaftfixed thereon, a control nut having a substantial counterbore at itsrear end and loosely threaded on said screw shaft to permit relativeinclination thereon, a, pinion slidably journalled on said power shaftfor engagement with and rotation of an engine gear, means including anoverrunning clutch for driving the pinion from the control nut, a memberhaving a, high coefiicient of friction located between said nut andscrew shaft in position to establish a, frictional connectiontherebetween when the nut is inclined on the screw shaft, and acentrifugally responsive mass on said control nut for causinginclination of the nut responsive to high speed rotation thereof.

JAMES E. BUXTON.

